1. Field of the Invention
This invention relates to a process of purifying gases which are produced by a partial oxidation of hydrocarbons by a treatment with steam and oxygen under pressure at temperatures of 1200.degree. to 1500.degree. C., comprising cooling the gases and scrubbing them to remove solid impurities. This invention especially relates to removal of metals which form carbonyls.
2. Discussion of the Prior Art
It is known to gasify solid or liquid fuels by a treatment with steam and oxygen under a pressure of 60 kg/cm.sup.2 absolute pressure and a temperature of 1500.degree. C. in order to produce a raw gas which consists mainly of hydrogen and carbon monoxide and may be used, e.g., for the synthesis of methanol. For purification, the raw gas is first cooled and freed from condensate, carbon black and water, and subsequently scrubbed with methanol at a temperature of -10.degree. C. to -30.degree. C. and a pressure up to 150 kg/cm.sup.2 so that sulfur compounds and carbon dioxide are substantially removed. A partial stream of the desulfurized raw gas may be subjected to a shift conversion treatment with steam in order to convert its carbon monoxide content to hydrogen and carbon dioxide and may subsequently be added to the scrubbed gas to adjust the latter to the CO:H.sub.2 ratio which is required for methanol synthesis. After a further purification stage, the gas can then be catalytically reacted to methanol (British Patent No. 1,164,407).
A similar process of producing a synthesis gas for the production of ammonia has also been described. In that process, solid or liquid fuel is also gasified by a treatment with oxygen and steam to produce a raw gas, which is purified and is subsequently treated with steam to convert its carbon monoxide content into carbon dioxide and hydrogen. The carbon dioxide is scrubbed off and the resulting high-hydrogen gas is mixed with nitrogen in a ratio of N.sub.2 :3H.sub.2. The mixture is compressed to a suitable pressure so as to produce a gas which is suitable for the synthesis of ammonia (German Patent No. 1,231,222).
When these and similar processes of producing synthesis gases are carried out in existing plants, trouble is sometimes caused by deposits. To avoid this, the precooled gas must also be freed from sulfide-forming metal compounds and must be cooled further. A removal of hydrogen cyanide is also desired in order to decrease the expenditure involved in the subsequent purification of the gas. In that known process, a part of the metal impurities is inevitably converted to volatile metal carbonyls, which may adversely affect the succeeding gas-purifying plants or the usefulness of the gases for the intended purpose.
It is an object of the invention to avoid these and other disadvantages and to provide a process in which raw gas can be pre-purified in such a manner that after a simple treatment to remove sulfur and part of the carbon dioxide they can be used for a synthesis of chemical compounds, such as methanol and ammonia.
Specifically, the novel process is intended to prevent a formation of metal carbonyls in the gas, also to remove hydrogen cyanide, and to produce a gas which is free from these poison and can be processed further without trouble and is free from substances which tend to deteriorate catalysts used for such further processing.